Multilayer articles and methods for making multilayer articles

ABSTRACT

In one embodiment, a sheet, comprises: a cap layer comprising an acrylic polymer; and a base layer, where the cap layer and the base layer were co-extruded to form the sheet, which is thermoformable. The base layer comprises a polycarbonate. The cap layer is 10% to 30% of an overall thickness and the overall thickness is 5 mil to 500 mil.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patent application Ser. No. 12/020,634, filed Jan. 28, 2008, which is incorporated by reference herein in its entirety.

BACKGROUND

In-mold decorated thermoplastic films are gaining wide acceptance in applications such as household consumer electronics, appliances, and printed overlays. These applications demand a combination of properties such as clarity, printability, thermoformability, and hardness, as well as scratch, chemical, and impact resistance. This combination is not attainable with many materials of choice. The most common solution has been to apply a functional coating as a cap layer on thermoplastic films, wherein the coating offers the surface properties while the base film provides the bulk mechanical integrity. However, while a coating improves scratch resistance, it takes away the films thermoformability, which seriously restricts the useful applications for such a film. One of the most difficult challenges is the balance between scratch resistance and thermoformability.

Therefore, there remains a need in the art for multilayer sheets that can be easily formed, e.g., via co-extrusion, and which provide the desired combination of properties, including thermoformability and scratch resistance.

BRIEF SUMMARY

The present disclosure is generally directed to thermoformable materials, methods for making thermoformable sheets, and articles made therefrom. In one embodiment, the sheet, comprises: a cap layer comprising an acrylic polymer and a base layer comprising a polycarbonate. The cap layer and the base layer were co-extruded to form the sheet, which is thermoformable. The cap layer is 10% to 30% of an overall thickness and the overall thickness is 5 mil to 500 mil.

In another embodiment, a sheet comprises: a cap layer comprising an acrylic polymer and a base layer comprising a cycloaliphatic polyester copolymer and a polycarbonate. The cycloaliphatic polyester copolymer is poly(1,4-cyclohexylene dimethylene co-ethylene terephthalate). The base layer and the cap layer were co-extruded to form the sheet, which is thermoformable. The cap layer is 10% to 30% of an overall thickness and the overall thickness is 5 mil to 500 mil. The sheet has a pencil hardness greater than or equal to HB.

In one embodiment, a method for making an article can comprise: melting an acrylic polymer in an extruder, forming a molten mixture comprising a polycarbonate in an extruder, and co-extruding the acrylic polymer and the polycarbonate to form a sheet. The molten mixture forms a base layer and the acrylic polymer forms a cap layer on the base layer. The cap layer is 10% to 30% of an overall sheet thickness and the sheet has a pencil hardness greater than or equal to HB.

The disclosure can be understood more readily by reference to the following detailed description of the various features of the disclosure and the examples included therein.

BRIEF DESCRIPTION OF THE DRAWINGS

Refer now to the figures, which are merely illustrative, not limiting.

FIG. 1 is a cross-sectional illustration of a scratch created by a profile load.

FIG. 2 is a schematic of an exemplary co-extrusion system.

DETAILED DESCRIPTION

Multilayer articles comprise a cap layer and a base layer. The cap layer can be based on acrylic polymers such as those of alkyl(meth)acrylates (e.g., poly(methyl methacrylate) (PMMA)), while the base layer can be a combination of a cycloaliphatic polyester copolymer and an optional aromatic polycarbonate. The base layer can also comprise a polycarbonate. The cap layer and base layer can be co-extruded to form a multilayer sheet.

Hardness, scratch resistance, mechanical strength, and thermoformability of such articles should enable these articles to meet a desired combination of properties such as clarity, printability, thermoformability, and hardness, as well as scratch, chemical, and impact resistance. Additionally, the base layer adheres to the cap layer without the need for any adhesive or a tie layer, and provides a substantial rheology match between the cap layer and the base layer, thereby improving the processability of the composite film.

In one embodiment, the sheet, comprises: a cap layer comprising an acrylic polymer; and a base layer, wherein the sheet is thermoformable. The base layer comprises a cycloaliphatic polyester copolymer and optionally, an aromatic polycarbonate. The base layer can alternatively comprise a polycarbonate. The cycloaliphatic polyester copolymer can comprise greater than 10 wt % cycloaliphatic diol or acid or combination thereof, based upon a total weight of the cycloaliphatic polyester copolymer. The cap layer can be 1% to 50% of an overall thickness, specifically 10% to 30% of an overall thickness and the overall thickness can be 5 mil to 500 mil. The base layer can comprise a blend of 25 wt % to 100 wt % cycloaliphatic polyester, balance polycarbonate, or, specifically, 50 wt % to 90 wt % cycloaliphatic polyester, balance polycarbonate. The base layer can comprise a blend of 100 wt % polycarbonate. The sheet can have a pencil hardness greater than HB. The sheet can also have a pencil hardness greater than or equal to HB. The sheet having a pencil hardness greater than HB can further comprise a tear initiation strength of greater than or equal to 120 N/mm and/or a tear propagation strength above 5 N/mm, and/or a tensile strength greater than 40 MPa. The acrylic polymer can be an alkyl(meth)acrylate, or, specifically, poly(methyl methacrylate). The acrylic polymer can optionally include an impact modifier (e.g., the acrylic polymer can be impact modified poly(methyl methacrylate)). The base layer can comprise 20 wt % to 90 wt % PCCD, balance aromatic polycarbonate. The base layer can comprise 100 wt % polycarbonate.

In one embodiment, a sheet comprises: a cap layer comprising an acrylic polymer and a base layer comprising a polycarbonate, wherein the cap layer and the base layer were co-extruded to form the sheet, which is thermoformable. The cap layer is 10% to 30% of an overall thickness and the overall thickness is 5 mil to 500 mil. The sheet can have a pencil hardness greater than or equal to HB, specifically, greater than or equal to H. The base layer can also comprise a copolycarbonate or a cycloaliphatic polyester copolymer and a polycarbonate, wherein the cycloaliphatic polyester copolymer is poly(1,4-cyclohexylene dimethylene co-ethylene terephthalate). The cap layer can be on and in contact with the base layer. The overall thickness of the sheet can be 5 mil to 40 mil. The sheet can be thermoformed at a temperature below the glass transition temperatures of the acrylic polymer and the polycarbonate. The blend can comprise 20 wt % to 50 wt % cycloaliphatic polyester, balance polycarbonate. The acrylic polymer can comprise an alkyl(meth)acrylate and the alkyl(meth)acrylate can comprise a poly(methyl)methacrylate. The poly(methyl)methacrylate can have a haze value of less than or equal to 5% as tested per ASTM D1003-00.

In another embodiment, a sheet can comprise: a cap layer comprising an acrylic polymer and a base layer comprising a cycloaliphatic polyester copolymer and a polycarbonate, where the cycloaliphatic polyester copolymer is poly(1,4-cyclohexylene dimethylene co-ethylene terephthalate). The cap layer can be 10% to 30% of an overall thickness and the overall thickness can be 5 mil to 500 mil. The cap layer and the base layer can be co-extruded to form the sheet which is thermoformable. The sheet can have a pencil hardness greater than or equal to HB. The acrylic polymer can comprise an alkyl(meth)acrylate, specifically, the acrylic polymer can comprise poly(methyl)methacrylate.

In one embodiment, a method for making an article can comprise: melting an acrylic polymer in an extruder, forming a molten cycloaliphatic polyester copolymer in an extruder, and co-extruding the acrylic polymer and the cycloaliphatic polyester copolymer to form a sheet. The cycloaliphatic polyester copolymer can comprise an amount of greater than 10 wt % cycloaliphatic polyester, based upon a total weight of the cycloaliphatic polyester copolymer. The cycloaliphatic polyester copolymer can form a base layer and the acrylic polymer forms a cap layer on the base layer. The sheet can be thermoformed.

In another embodiment, a method for making an article can comprise melting an acrylic polymer in an extruder, forming a molten mixture comprising a polycarbonate, and co-extruding the acrylic polymer and molten mixture to form a sheet which is thermoformable. The molten mixture can form a base layer and the acrylic polymer can form a cap layer on the base layer. The cap layer can be 10% to 30% of an overall sheet thickness and the sheet can have a pencil hardness greater than or equal to HB. The sheet can be thermoformed at a temperature below the glass transition temperatures of the acrylic polymer and the polycarbonate. The acrylic polymer can comprise an alkyl(meth)acrylate, specifically, poly(methyl methacrylate). The overall sheet thickness can be 5 mil to 40 mil, specifically, 3 mil to 40 mil. The cap layer can be co-extruded on and in contact with the base layer.

The cycloaliphatic polyesters have the formula:

wherein R¹³ and R¹⁴ are independently at each occurrence an aryl, aliphatic or cycloalkane having 2 to 20 carbon atoms, with the proviso that at least one of R¹³ and R¹⁴ is a cycloaliphatic group. The cycloaliphatic polyester is a condensation product where R¹³ is the residue of a diol or a chemical equivalent thereof and R¹⁴ is residue of a diacid or a chemical equivalent thereof. In one embodiment, both R¹³ and R¹⁴ are cycloalkyl-containing groups. Such polyesters generally contain at least 50 mole % of cycloaliphatic diacid and/or cycloaliphatic diol components, the remainder, if any, being aromatic diacids and/or linear aliphatic diols.

In one embodiment R¹³ and R¹⁴ are cycloalkyl radicals independently selected from the following structural units:

In a specific embodiment the diol is 1,4-cyclohexane dimethanol or a chemical equivalent thereof. Either or both of the cis or trans isomers of the 1,4-cyclohexane dimethanol can be used. Chemical equivalents to the diols include esters, such as C₁₋₄ dialkylesters, diaryl esters, and the like. Specific non-limiting examples of diacids include decahydro naphthalene dicarboxylic acids, norbornene dicarboxylic acids, bicyclo octane dicarboxylic acids, 1,4-cyclohexanedicarboxylic acid or the chemical equivalents thereof. Most specifically the diacids include trans-1,4-cyclohexanedicarboxylic acid or a chemical equivalent thereof. Chemical equivalents of these diacids include C₁₋₄ dialkyl esters, diaryl esters, anhydrides, salts, acid chlorides, acid bromides, and the like. In one embodiment the chemical equivalent comprises the dialkyl esters of the cycloaliphatic diacids, and most specifically the dimethyl ester of the acid, such as dimethyl-1,4-cyclohexane-dicarboxylate.

Other types of units can be present in the cycloaliphatic polyester copolymer, including units derived from the reaction of an aromatic carboxylic diacid component and a non-cycloaliphatic diol, or chemical equivalents thereof. Exemplary aromatic dicarboxylic acids include isophthalic acid, terephthalic acid, 1,2-di(p-carboxyphenyl)ethane, 4,4′-dicarboxydiphenyl ether, 4,4′-bisbenzoic acid, 1,4-, 1,5-, or 2,6-naphthalenedicarboxylic acids, and combinations comprising at least one of the foregoing acids. Specific dicarboxylic acids are terephthalic acid, isophthalic acid, and combinations comprising the two foregoing acids. The non-cycloaliphatic diol can be a C₁₋₄ alkylene glycol, for example ethylene glycol, propylene glycol, 1,4-butylene glycol, and the like, and combinations comprising at least one of the foregoing glycols.

The cycloaliphatic polyester copolymers more specifically comprise at least 50 mole % of the cycloaliphatic residues, more specifically at least 70 mole % of the cycloaliphatic residues, the remainder being the aromatic acid or C₁₋₄ alkylene glycol residues. A specific cycloaliphatic polyester is poly(cyclohexane-1,4-dimethylene cyclohexane-1,4-dicarboxylate), also referred to as poly(1,4-cyclohexane-dimethanol-1,4-dicarboxylate) (PCCD). Another specific ester is poly(1,4-cyclohexylene dimethylene co-ethylene terephthalate) (PCTG) wherein greater than 50 mol % of the ester groups are derived from 1,4-cyclohexanedimethanol; and poly(ethylene-co-1,4-cyclohexylenedimethylene terephthalate) wherein greater than 50 mol % of the ester groups are derived from ethylene (PETG). Also contemplated for use herein are any of the above polyesters with minor amounts, e.g., from 0.5 to 5 percent by weight, of units derived from aliphatic acid and/or aliphatic polyols to form copolyesters. The aliphatic polyols include glycols, such as poly(ethylene glycol) or poly(butylene glycol).

Aromatic polycarbonates are of the formula:

in which at least 60 percent of the total number of R¹ groups are an aromatic organic radical and the balance thereof are aliphatic, alicyclic, or aromatic radicals. The term “polycarbonate” as used herein includes copolycarbonates, that is, copolymers comprising two or more different R¹ groups. In one embodiment, each R¹ is derived from a bisphenol compound of the formula:

wherein R^(a) and R^(b) are each a halogen atom or a monovalent hydrocarbon group and can be the same or different; p and q are each independently integers of 0 to 4; and X^(a) represents one of the groups of the formulas:

wherein R^(c) and R^(d) each independently represent a hydrogen atom or a monovalent linear or cyclic hydrocarbon group and R^(e) is a divalent hydrocarbon group.

Specific examples of bisphenol compounds include 1,1-bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane (hereinafter “bisphenol A” or “BPA”), 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, 1,1-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)n-butane, 2,2-bis(4-hydroxy-1-methylphenyl)propane, 1,1-bis(4-hydroxy-t-butylphenyl)propane, 3,3-bis(4-hydroxyphenyl)phthalimidine, 2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (PPPBP), and 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (DMBPC). Combinations comprising at least one of the foregoing bisphenol compounds can also be used. For example, copolymer can be used, comprising a mixture of units derived from bisphenol A and 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane.

In a specific embodiment, the polycarbonate is a linear homopolymer derived from bisphenol A, in which p and q are each zero, and Y¹ is isopropylidene. In one embodiment, the base layer comprises polycarbonate. The base layer can comprise linear polycarbonate or an aromatic polycarbonate as herein described.

The relative amount of the cycloaliphatic polyester component and aromatic polycarbonate components varies with the specific application. In one embodiment, the amount of the polyester component is in an amount of greater than 10 wt %, e.g., 25 wt % to 100 wt %, with the remainder being aromatic polycarbonate. In another embodiment, the amount of cycloaliphatic polyester is 50 wt % to 90 wt %, with the remainder being aromatic polycarbonate. The base layer composition is commercially available from SABIC Innovative Plastics IP B.V. as XYLEX*. In another embodiment, the polycarbonate component is 100 wt %.

The cap layer can be based on acrylic polymers such as those of alkyl(meth)acrylates (e.g., poly(methyl methacrylate) (PMMA)). This layer can comprise greater than or equal to 50 wt % acrylic polymer, or, specifically, greater than or equal to about 70 wt % acrylic polymer, or, more specifically, greater than or equal to about 90 wt % acrylic polymer, based upon a total weight of the cap layer. The remainder can be any other polymer that, when blended with the acrylic polymer, results in a cap layer with a transmission of greater than or equal to 80% or a haze value of less than or equal to 5%, specifically, less than or equal to 3%, or more specifically, less than or equal to 1%, as is determined in accordance with ASTM D1003-00, Procedure A measured, e.g., using a HAZE-GUARD DUAL from BYK-Gardner, using and integrating sphere (0°/diffuse geometry), wherein the spectral sensitivity conforms to the CIE standard spectral value under standard lamp D65. The acrylic polymer can further comprise an impact modifier provided that the impact modifier does not interfere with the transmission or haze of the cap layer.

In addition to the above materials, the base layer and/or cap layer can, independently, include various additives, with the proviso that the additives are selected so as to not significantly adversely affect the desired properties of the layers, for example, thermoformability, scratch resistance, and so forth. Combinations of additive(s) can be used. Such additives can be mixed at a suitable time during the mixing of the components for forming the composition for each of the layers. Possible additive(s) include anti-oxidants, flame retardants, drip retardants, dyes, pigments, colorants, stabilizers (e.g., thermal, ultraviolet, and so forth), small particle mineral (such as clay, mica, and/or talc), antistatic agents, plasticizers, lubricants, mold release agents, whitening agents, impact modifiers, reinforcing fillers (e.g., glass), and combinations comprising at least one of the foregoing. The amount of additive(s) can be less than or equal to about 20 wt %, or, specifically, about 0.1 wt % to about 10 wt % additive(s), or, more specifically, about 0.5 wt % to about 5 wt % additive(s), based upon a total weight of the layer comprising the additive(s).

In some embodiments, the sheet can additionally comprise a coating on either side of the base layer or the cap layer (e.g., disposed across the length and/or width). The coating on the base layer and/or the cap layer can comprise the same material or can comprise different materials. The coating can comprise any material that will not adversely impact the desired properties of the sheet (e.g., light transmission, scratch resistance, etc.). The coating can provide abrasion resistance, chemical resistance, pencil hardness, and other physical properties to the sheet. The coating can be an ultraviolet (UV) cure coating or a thermal cure coating and can be solvent based or solventless. The coating can be selected such that it has flexibility after curing so that the co-extruded sheet after application of the coating can then be formed (e.g., thermoformed) into the desired shape for applications such as in mold decoration. The coating can be applied to the sheet using methods such as, but not limited to, reverse roll, gravure roll, spray coating, and slot die coating. Alternatively, the coating can be partially cured (e.g., by thermal methods), the sheet formed into the desired shape, and then the coating cured (e.g., with actinic energy). In another embodiment, the coating (e.g., UV cure or thermal cure) can be applied to the sheet after it has been formed (e.g., thermoformed) in a separate operation such as spray coating.

The present cap layer and base layer are formed by co-extrusion. For example, the multi-layer composite can be suitably formed using a continuous calendaring co-extrusion process as shown schematically in FIG. 2. In this process, single screw extruders 1 and 2 supply resin melts for the individual layers (i.e., the top layer, the second layer and any additional polymeric layers) into a feed block 3. A die 4 forms a molten polymeric web that is fed to a 3 roll-calendaring stack 5. Typically, the calendaring stack comprises 2 to 4 counter-rotating cylindrical rolls with each roll, individually, made from metal (e.g., steel) or rubber coated metal. Each roll can be heated or cooled, as is appropriate. The molten web formed by the die can be successively squeezed between the calendaring rolls. The inter-roll clearances or “nips” through which the web is drawn determines the thickness of the layers. The multi-layer composite may also be formed from separate pre-formed films corresponding to the polymeric layers which are subsequently laminated together, for example using heated rolls and optionally adhesive tie layers.

The layers can be co-extruded to form various cap layer to base layer thickness ratios (i.e., cap layer thickness divided by base layer thickness). The thickness ratio can be 1% to 50%, or, specifically, 5% to 40%, or, more specifically, 10% to 25%. Generally, the overall thickness of the sheet can be up to and even exceeding several millimeters. More specifically, the sheet can have a thickness (e.g., gage) of 1 mil (25.4 micrometers (μm)) to 500 mils (1,2700 μm), or, yet more specifically, about 5 mils (127 μm) to about 40 mils (1016 μm), and yet more specifically, about 5 mils (127 μm) to about 30 mils (762 μm). In some embodiments, the cap layer can comprise a thickness that is 10% to 30% of an overall sheet thickness, specifically, 5% to 10%, more specifically, 1% to 5%, even more specifically, 0.5% to 2%, and still more specifically, 0.1% to 3%. The overall sheet thickness can be 5 mil to 500 mil, specifically, 3 mil to 20 mil, more specifically, 10 mil to 15 mil, and even more specifically, 5 mil to 10 mil. The cap layer can comprise a thickness of 10 mil to 15 mil, specifically, 0.5 mil to 5 mil, more specifically, 1 mil to 2 mil, and even more specifically, 0.5 mil to 1 mil.

The sheet can be thermoformed after co-extruding the cap layer and the base layer. Thermoforming can be performed at temperatures below the glass transition temperatures of the materials of the cap layer and the base layer. This has advantages in allowing the use of a single manifold die to produce the sheet. For example, thermoforming can be performed at temperatures less than or equal to 100° C., specifically less than or equal to 95° C., more specifically, less than or equal to 85° C., and even more specifically, less than or equal to 75° C.

The following examples are merely exemplary, not limiting.

EXAMPLES Example 1

Bilayer films of varying cap layer compositions and film constructions (Samples 1 through 13 in Table 2) were prepared using the co-extrusion method described in relation to FIG. 2. The specific process parameters for each sample varied with individual layer thicknesses and the overall film thickness, the range of process parameters encompassing all samples in Table 2 is given in Table 3. It is understood that the process window for extruding these films is not restricted to that listed in Table 3. An objective of this experiment was to determine whether or not there exists “a” condition at which these co-extruded films could be made, i.e. whether or not these films are extrudable. Table 3 merely provides one set of conditions for co-extruding these films.

This example demonstrates the suitability of the disclosed articles for in mold decoration (IMD) applications. Films for such applications should be amenable to the three sub-processes of IMD: (a) extrudability—ability to make films out of the selected materials, at a surface quality comparable to commercially available polished graphic films (e.g., Lexan* 8010 film); (b) formability—ability to draw the films into different geometries; and (c) trimming—ability to cut the film cleanly without inducing any cracking or delamination.

Table 1 contains the chemical description and the source of the resins used in the film constructions set forth in Table 2.

TABLE 1 Component Chemical Description Source/Vendor PC Polycarbonate resin (Mw¹ = 25,000 SABIC Innovative g/mol, PS standards²) Plastics, Pittsfield, MA PCTG Poly(20 mole % ethylene Eastman Chemical, terephthalate)-co-(80 mole % 1,4 Kingsport, Tenn. cyclohexanedimethylene terephthalate) (Mw = 70,000 g/mol, PS standards) PCCD Poly(1,4-cyclohexanedimethylene Eastman Chemical terephthalate) 1,4- Kingsport, Tenn. cyclohexanedimethanol PMMA Poly(methyl methacrylate) Arkema Philadelphia, PA ¹Mw = weight average molecular weight ²PS standards = as measured by gel permeation chromatography (GPC)

Table 2 evaluates the samples along the above 3 attribute metrics: surface quality, thermoformability, and trimming. To measure surface quality, 10 pieces of size 12 inches×12 inches (30.5 cm×30.5 cm) were examined by 3 operators to identify any imperfection (lines, dents, bumps) of length scales greater than 2 mm Absence, to the unaided eye, of any such imperfection was considered a “pass”. It was not intended to test the optical quality of the films, but instead meant to identify any gross imperfections suggesting any issues with film co-extrusion.

To test the formability 12 inches×12 inches specimens of the film were preheated to 140° C. and then vacuum formed on a COMET Thermoformer, with the male forming tool at 120° C., a minimum curvature of 5 mm, and maximum draw of 10 mm A “pass” on this test is absence of any wrinkle, whitening, or tear on the film during the process as determined with an unaided eye. (The unaided eye excludes the use of optical devices for magnification with the exception of corrective lenses needed for normal eyesight.)

The formed parts were trimmed using matched metal dies comprising hardened male and female die halves (American Iron and Steel Institute “AISI” Type A2 steel), with a clearance between the male die half and female die half of 10% of sheet thickness; wherein the part is at a 90 degree angle to the blade at the time of impact. Trimming the thermoformed part is an integral step in the IMD process. Multilayer structures with poor interlayer adhesion tend to delaminate during this step. A pass on this test is absence of any visible signs of cracking and any visible delamination during this step, with visibility determined with an unaided eye.

TABLE 2 Pencil Formability Trimming Hardness Base layer Surface (>10 mm (Cracking/ (ASTM No. Cap % Composition Quality draw) delamination) D3363-05) 1 0 60/40 PCTG/PC Pass Pass Pass 2B 2 10 60/40 PCTG/PC Pass Pass Pass 2H 3 30 60/40 PCTG/PC Pass Pass Pass 3H 4 50 60/40 PCTG/PC Pass Pass Fail 4H 5 20 0/100 PCTG/PC Pass Pass Fail 2H 6 10 0/100 PCTG/PC Fail Fail Fail — 7 20 25/75 PCTG/PC Pass Pass Pass 2H 8 20 80/20 PCTG/PC Pass Pass Pass 2H 9 20 100/0 PCTG/PC Pass Pass Pass 2H 10 10 30/70 PCCD/PC Pass Pass Pass  H 11 10 60/40 PCCD/PC Pass Pass Pass 2H 12 10 80/20 PCCD/PC Pass Pass Pass  H 13 10 100/0 PCCD/PC Fail Fail Fail —

TABLE 3 Main Extruder diameter 1.75 inches Co-extruder Diameter 1.25 inches Main Extrude End Zone Temp (° F.) 479° to 491° Co-extruder End Zone Temp (° F.) 463° to 476° RPM (Main/Co-ex) (46.5 to 50.5)/(4.4 to 6.7) Die Temp (° F.) 506° to 510° Roll Temp (Top/Bottom) (° F.) (198° to 209°)/(205° to 216°)

Table 2 leads to the following conclusions: (1) co-extruded films show a marked improvement in hardness, even 10% cap takes the hardness upward of H; (2) while increasing the cap thickness improves the pencil hardness, it makes the film brittle as is seen from the trimming performance (Sample 4, while it exhibited a pencil hardness of 4H, cracked during the trimming process, and hence is unsuitable for IMD); (3) polyester in the base layer makes the film IMD friendly (100% PC in the base layer poses challenges for co-extrusion with the cap layer). At 10% cap thickness (Sample 6), the film could not be extruded, while the film did get co-extruded at a higher cap to base ratio (Sample 5), it failed the trimming test wherein it led to delamination between the cap and base layers; and (4) depending on the type of polyester, blending with PC may be useful, e.g., in a weight ratio of 0% to 20% or more, based upon a total weight of the base layer, e.g., to facilitate co-extrusion. While 100% PCTG as the base layer was extrudable, PCCD was blended with PC to enable extrusion. Hence, if PCCD is employed, the base layer can comprise 20 wt % to 90 wt % PCCD, or, specifically, 30 wt % to 80 wt % PCCD, or, more specifically, 40 wt % to 60 wt % PCCD, balance PC. Additionally, the cap thickness can be 1% to 50%, or, specifically, 5% to 40%, or, more specifically 10% to 30%, and yet more specifically, 15% to 25%.

Example 2

This example demonstrates hardness and scratch resistance of the multilayer film. Two samples were prepared in accordance with the film and resin composition set forth in Table 4. These samples were prepared the same way as those of Example 1. Sample 14 is essentially a monolayer film, included in this comparison to highlight the performance improvement brought about by the cap layer.

TABLE 4 Base layer No. Cap % Composition 14 0 60/40 PCTG/PC 15 10 60/40 PCCD/PC 16 10 60/40 PCTG/PC

The two samples were compared to three commercially available samples for graphic applications: a 2 layer co-extruded polycarbonate film where the cap is a PC copolymer while the base is PC (specifically Lexan* ML 9735 commercially available from SABIC Innovative Plastics, Pittsfield, Mass.) (Sample 17) (known as 1HD00, commercially available from SABIC Innovative Plastics); a monolayer polycarbonate (Sample 18) polycarbonate (Lexan* 8010, commercially available from SABIC Innovative Plastics); and a coated polycarbonate film (Sample 19) comprising a curable silica coating on a base of polycarbonate (specifically Lexan* 8010) (known as HP92S, commercially available from SABIC Innovative Plastics), all commercially available from SABIC Innovative Plastics. It must be noted that HP92S is a coated film which is not formable.

All samples were tested for hardness, namely pencil hardness according to ASTM D3363-05. Both of Samples 15 and 16 had a pencil hardness of 2H, while Samples 17, 18, and 19 had lower hardness: 1H, 2B, and HB, respectively. Sample 14 had a hardness of 2B, which highlights the significance of the cap layer.

The samples were also tested for scratch resistance using an Erichsen Scratch Tester Type 413, which complies with ISO 1518. Forces of 2 Newtons (N) and 4N were applied to a conical stylus with radius of 0.01 millimeter (mm), which result in an indentation being made on the part surface. The extent of the indentation is subsequently measured by a Dektak 6M profilometer and is reported as the height of the indentation measured from the bottom of the indentation to the sample surface. Again, Samples 15 and 16 outperformed the comparative samples. Sample 15 and 16 had scratch depths of 1.15 micrometers (μm) and 1.25 μm, respectively. The comparative samples had scratch depths of 1.4 μm, 2.86 μm, and 2.95 μm, respectively. The sample without any cap layer (Sample 14) had a scratch depth of 3.02 micrometers (μm).

The data generated in Samples 14-16 was generated under heavy loading. In yet another instance as shown in Table 5, micro-scratch tests (light loading) were performed with a Nano Indenter XP, MTS Systems, applying a normal load ramping from 0 to 50 milliNewtons (mN). The scratch velocity was 50 micrometers per second (μm/s). A standard Berkovich diamond indenter (with 10 nanometer (nm) radius tip) was used which was moved edge forward through the material. FIG. 1 is an illustration of one such scratch and the corresponding measured cross profile showing the build-up around the scratch. Reported below is the instantaneous depth (depth during) of the profile at the point when the load reaches 25 mN. This gives a measure of softness/hardness of the material. By the time the entire scratch is made (load reaches 50 mN), some of the disturbed material along the scratch has recovered, as a result of which the scratch depth reduces. The depth and width of the scratch is measured again at the same point as above. This is “depth after”. This gives a measure of recovery (“forgiveness”) of the material.

TABLE 5 Lexan* 1HD00 8010 HP92S Property Sample 14 Sample 15 Sample 16 (Sample 17) (Sample 18) (Sample 19) Width (μm) 33.31 22.067 22.087 26.352 32.477 25.21 Depth-during 4872 3735 3725 4167 4690 4925 (nm) Depth-after 1921 1090 1130 1320 1875 955 (nm)

Table 5 further emphasizes the scratch resistance improvement resulting from the bilayer construction (Samples 14 vs. 15/16). Not only do Samples 15 and 16 perform better than Samples 17 and 18, they are also comparable to the coated comparative sample HP92S (Sample 19). This is unexpected since one would have expected the coatings, by virtue of their cross-linking, to be much more resistant under such light loading

In addition to scratch resistance and hardness, mechanical robustness is also a factor for IMD applications; e.g., the film should be resistant to cracks and tears. Table 6 reports the tear initiation and propagation strengths in Newtons per millimeter (N/mm) as measured using ASTM D1004-03, ASTM D1938-02, and ASTM D882, respectively.

TABLE 6 1HD00 Lexan* 8010 HP92S Property Sample 15 Sample 16 (Sample 17) (Sample 18) (Sample 19) Tear Initiation 206.1 ± 10.1 171.8 ± 26.3 234.29 ± 7.4  241.19 ± 11.2  258.41 ± 6.7  Strength (N/mm) Tear Propagation 15.48 ± 0.84 15.12 ± 2.9  10.05 ± 0.77 9.2 ± 0.8 10.52 ± 0.6 Strength (N/mm) Tensile Strength 60.08 62.4 60.7 58.6 59.3 at break (MPa)

It is evident from Table 6 that the improved scratch resistance and hardness as seen in the previous examples, did not compromise the mechanical properties of the articles.

Example 3

This example demonstrates the hardness and foldability of multilayer sheets. Table 7 lists the properties for the PMMA (i.e., cap layer) used in this example, while Table 8 lists the material properties for the various materials used for the base layer of the sheet. Grade ZK5BR PMMA from Evonik is impact modified PMMA as is grade DR101 from Arkema. Grade V020 from Arkema is general purpose PMMA, while grade HT121 from Arkema is a high heat resistant PMMA. The properties were determined on injected specimens having a thickness of 3.2 mm Heat Deflection Temperature (HDT) was determined at a pressure of 1.82 megaPascals (MPa). Table 8 lists the material properties for the polycarbonates used in this example. Three different grades of XYLEX, a PC/PCTG copolymer were used where the amount of PCTG weight percent used in the copolymer are displayed in Table 8 with the remainder being polycarbonate (PC). For example, Grade X7509 contains 26.30 weight % PCTG, balance PC (i.e., 74.70 weight % PC).

TABLE 7 Pencil Izod Multi-axial Trans. (%) Haze (%) Hardness HDT Impact impact Total Before Before Before Supplier Grade (° C.) (J/m) energy (J) coating coating coating Evonik ZK5BR 90.4 41.2 4.18 ± 0.70 92.9 ± 0.07 3.05 ± 0.42 1-2H   DR101 83.7 49.1 11.9 ± 5.7  91.8 ± 0.13 4.05 ± 0.21  H Arkema V020 94 24.1 2.86 ± 0.93 9.38 ± 0.05 1.88 ± 0.26 3H HT121 105 18.5 2.44 ± 0.18 93.6 ± 0.04 0.94 ± 0.07 4H

TABLE 8 HDT, Izod 1.82 Mpa Light Notched Vicat @3.2 mm Transmission @23° C. B/120 (° C., (Haze) (%, (J/m, PCTG (° C., ASTM ASTM ASTM Grade Weight % ISO306) D648) D1003) D256) MFR @265° C./ 2.16 Kg (g/10 min, ASTM D1238) XYLEX X7509 26.30%   126 106 12  88 (2) 854 (PC/PCTG) X8419 48% 115 98 6 89 (2) 750 X8409 36% 123 104 4 88 (1.5) 854 MFR @300° C./ 2.16 Kg (g/10 min, ASTM D1238) HFD1014 131 115 7 88 (<1) 966 ML9736 150 124   6.3 908

Table 9 lists the various combinations of cap and base layers used in forming the sheets, the total thickness of the sheet, and the thickness of the cap layer. Pencil hardness was measured according to ASTM D3363-05 and folding behavior was observed. Folding behavior refers to the ability of the sheet to be folded where if the sheet cracks, breaks, or delaminates, it receives a “poor” rating, while if the sheet does not crack or break, it receives a rating of “excellent”. A rating of “good” applies when the sheet is able to be folded but some cracking is observed. As can be seen in Table 9, the use of impact modified PMMA in the cap layer combined with the use of a PC/PCTG copolymer for the base layer gave a pencil hardness of greater than or equal to HB and “excellent” folding behavior (e.g., Samples 1-6). For example, a pencil hardness of greater than or equal to HB can be achieved with a cap layer thickness of greater than or equal to 25 micrometers, specifically, greater than or equal to 27 micrometers, more specifically, greater than or equal to 30 micrometers, even more specifically, greater than or equal to 35 micrometers, and still more specifically, greater than or equal to 40 micrometers.

With the use of general PMMA in Comparative Samples 1 to 6 (C1 to C6 in Table 9), the pencil hardness was acceptable, but the folding behavior was not, with all three sheets being broken. Similar results were observed in Samples 7 to 12, 15, and 16 where polycarbonate (i.e., Lexan* ML 9736, which is a proprietary grade of SABIC Innovative Plastics IP B.V.) was used for the base layer. In these examples, the use of impact modified PMMA in the cap layer (e.g., Samples 7 to 12) provided a pencil hardness greater than or equal to HB and “excellent” folding behavior at a cap layer thickness of greater than or equal to 20 micrometers, specifically, greater than or equal to 25 micrometers, more specifically, greater than or equal to 30 micrometers, and even more specifically, greater than or equal to 40 micrometers. Samples 13 to 16 demonstrate that the use of high heat resistant PMMA with either PC/PCTG or PC at a cap layer thickness of greater than or equal to 14 micrometers, gives a pencil hardness of greater than or equal to H and “good” folding behavior.

TABLE 9 Cap layer Cap layer Pencil Total Designed Measured Hardness Folding Sample No. Resins used gauge (μm) (μm) @500 g behavior C1 V020/X8419 7 mil 25.4 22.7 F Poor (broken) C2 V020/X8419 7 mil 38.1 30.9 2H Poor (broken) C3 V020/X8419 7 mil 50.8 37.5 3H Poor (broken) 1 ZK5BR/X8419 7 mil 25.4 23.6 F Excellent 2 ZK5BR/X8419 7 mil 38.1 31.3 H Excellent 3 ZK5BR/X8419 7 mil 50.8 42.2 H Excellent 4 DR101/X8419 7 mil 25.4 25.3 HB Excellent 5 DR101/X8419 7 mil 38.1 27.1 HB Excellent 6 DR101/X8419 7 mil 50.8 38.5 F Excellent C4 V020/ML9736 7 mil 25.4 22.9 F Poor (broken) C5 V020/ML9736 7 mil 38.1 32.9 H Poor (broken) C6 V020/ML9736 7 mil 50.8 42.2 3H Poor (broken) 7 ZK5BR/ML9736 7 mil 25.4 21.8 HB Excellent 8 ZK5BR/ML9736 7 mil 38.1 22.4 HB-F Excellent 9 ZK5BR/ML9736 7 mil 50.8 43.0 H Excellent 10  DR101/ML9736 7 mil 25.4 23.6 2B-B Excellent 11  DR101/ML9736 7 mil 38.1 27.7 B-HB Excellent 12  DR101/ML9736 7 mil 50.8 33.5 HB Excellent 13  HT121/X8409 7 mil 16 14.7 F-1H Good 14  HT121/X8409 10 mil  16 14.9 1H Good 15  HT121/ML9736 7 mil 16 14.0 F-1H Good 16  HT121/ML9736 10 mil  16 14.7 F-1H Good

Example 4

Multilayer sheets were made comprising the compositions listed in Table 10 for the cap layer and the base layer. The forming temperature for the sheets post co-extrusion was 90° C. to 105° C. Table 10 illustrates that with the use of a high heat resistant PMMA cap layer (e.g., HT121) with a copolymer of PC/PCTG base layer, pencil hardness values of greater than or equal to H can be observed with a cap layer thickness of about 15 micrometers to about 23 micrometers. However, to achieve a rating of “good” for the folding behavior, the cap layer thickness was greater than or equal to 14 micrometers, specifically, greater than or equal to 15 micrometers, and more specifically, greater than or equal to 16 micrometers (e.g., Samples 1, 4, and 7). This result was surprising, considering that the amount of PCTG varied from 26 wt %, balance polycarbonate to 48 wt % PCTG, balance polycarbonate in Samples 1 to 9. Samples 1 to 3 comprised 48 wt % PCTG, balance PC, Samples 4 to 6 comprised 36 wt % PCTG, balance PC, and Samples 7 to 9 comprised 26.3 wt % PCTG, balance PC. It was surprising to observe that the folding behavior of the sheet was “good” when the cap layer thickness was less than or equal to 20 micrometers. When polycarbonate was used as the base layer (e.g., Samples 10 to 12 comprising Lexan* HFD1014, commercially available from SABIC Innovative Plastics IP B.V.) a pencil hardness of greater than or equal to H was achieved with a good folding behavior rating for all thicknesses of cap layer tested.

Samples 13 to 18 illustrate that with the use of an impact modified PMMA in the cap layer, using either a copolymer of PC/PCTG or PC for the base layer, a hardness rating of greater than or equal to H was achieved along with excellent folding behavior. These results indicate a synergistic effect between the cap layer and the base layer when the cap layer thickness is greater than or equal to 25 micrometers, specifically, greater than or equal to 30 micrometers, more specifically, greater than or equal to 35 micrometers, even more specifically, greater than or equal to 40 micrometers, still more specifically, greater than or equal to 45 micrometers, and even still more specifically, less than or equal to 50 micrometers.

TABLE 10 Designed cap Pencil Measured cap Sample Cap/Base Layer layer thickness Hardness Layer Folding No. Formulation (μm) @500 g thickness (μm) behavior 1 HT121/X8419 14 H 16.2 Good 2 HT121/X8419 17 H 20.8 Broken 3 HT121/X8419 20 2H  22.6 Broken 4 HT121/X8409 14 H 15.7 Good 5 HT121/X8409 17 H 20.4 Broken 6 HT121/X8409 20 2H  22.0 Broken 7 HT121/X7509 14 H 14.6 Good 8 HT121/X7509 17 H 18.0 Broken 9 HT121/X7509 20 H 20.8 Broken 10 HT121/HFD1014 14 F 15.8 Good 11 HT121/HFD1014 17 H 18.1 Good 12 HT121/HFD1014 20 H 21.1 Good 13 ZK5BR/X8419 30 F 29.1 Excellent 14 ZK5BR/X8419 40 H Excellent 15 ZK5BR/X8419 50 H 48.3 Excellent 16 ZK5BR/ML9736 30 H 28.6 Excellent 17 ZK5BR/ML9736 40 H 38.2 Excellent 18 ZK5BR/ML9736 50 H 46.31 Excellent

Example 5

In this example, multilayer sheets were prepared for an in mold decoration (IMD) process and the samples tested for cracking or delamination after the IMD process and after thermal cycling. Table 11 lists the formulations for the sheets, while Tables 12 and 13 list the forming conditions for the sheets and the injection molding conditions respectively. In this example, an impact modified PMMA (i.e., Arkema PMMA DR101) was back injected onto the base layer side of the multilayer sheet, opposite the side in contact with the cap layer. The forming machine was a Hsin-Chi 200 Ton high pressure forming machine, while the injection molding machine was a Krauss-Maffei 50 megaTon machine. Different thickness cap layer and base layers were tested as well as varying compositions of the base layer. The base layer of Samples 1 to 8 comprised a copolymer of PC/PCTG, while the base layer of Samples 9 and 10 comprised a polycarbonate. The cap layer of Samples 1 to 6 and Sample 9 and 10 comprised high heat resistant PMMA, while the cap layer of Samples 7 and 8 comprised impact modified PMMA. Table 14 lists the results from the cracking tests conducted before thermal cycling and after thermal cycling. After forming and back injection molding, the samples were subject to thermal cycling under the following conditions using a thermal oven (TSG3055W from GZ Espec Environment Instrument Ltd.). The testing sample was placed in the oven at a starting temperature of 40° C. for 45 minutes. The temperature was then increased to 80° C. for another 45 minutes for a total cycle time of 90 minutes. The above described cycle was then repeated 26 times for a total of 27 thermal cycles per sample.

TABLE 11 Cap/Base Layer Total Sheet Cap Layer Base Layer Thickness SampleNo. Composition Thickness (mil) Thickness (mil) (mil) 1 HT121/X8419 7 0.551 6.449 2 HT121/X8419 7 0.669 6.331 3 HT121/X8409 7 0.551 6.449 4 HT121/X8409 7 0.669 6.331 5 HT121/X7509 7 0.551 6.449 6 HT121/X7509 7 0.669 6.331 7 ZK5BR/X8419 7 1.146 5.854 8 ZK5BR/X8419 7 1.901 5.099 9 HT121/HFD1014 7 0.551 6.449 10 HT121/HFD1014 7 0.669 6.331

TABLE 12 Sheet Forming Conditions Top Mold Temp. (° C.) 140 Bottom Mold Temp. (° C.) 90/100/110 Bake Time (s) 20 1^(st) Pressure (kgf/cm²) 45 Pressure Charge Time (s) 2 Hold Time (s) 6 2^(nd) Pressure (kgf/cm²) 55 Pressure Charge Time (s) 2 Hold Time (s) 6 IR heating No Vacuum No

TABLE 13 Injection Molding Conditions Material DR101 Melt temperature (° C.) 250 > 250 > 240 > 230 Mold temperature (° C.) 50 Injection Speed (m/s) 65 Packing Pressure (bar) 1200 Packing Time (s) 0.5 Cooling Time (s) 9 Back Pressure (bar) 8 Screw Speed (rpm) 50

TABLE 14 Forming Before Thermal After Thermal Sample. Temperature Cycling Cycling No. (° C.) Cracking % Cracking % 1 90 74 100 1 100 0 10 1 110 14 75 2 90 90 100 2 100 5 84 3 90 40 80 3 100 5 25 3 110 10 36 4 90 44 94 4 100 10 50 5 90 20 90 5 100 20 55 5 110 14 36 6 90 60 100 6 100 10 50 7 75 0 0 7 85 0 0 7 95 0 10 8 75 0 0 8 85 0 0 8 95 0 0 9 90 30 80 9 100 25 65 10 90 21 74 10 100 45 100 10 110 3 34

As is observed in Table 14, a multilayer sheet comprising a high heat resistant PMMA cap layer (e.g., HT121) and a base layer comprising a copolymer of PC/PCTG where the PCTG is present in the copolymer in an amount of 48 wt %, balance polycarbonate can be processed at about 100° C. with an extremely low cracking percent even after thermal cycling (e.g., Sample 1 at a forming temperature of 100° C.). Similar results were observed for a combination of a PMMA cap layer and a base layer comprising a copolymer of PC/PCTG where the PCTG is present in the copolymer in an amount of 36 wt %, balance polycarbonate (e.g., Sample 3 at a forming temperature of 100° C.). Samples 7 and 8, which comprised a cap layer comprising impact modified PMMA showed an even greater improvement in the cracking behavior before and after thermal cycling. Both Samples 7 and 8 demonstrated, at forming temperatures as low as 75° C., 0% cracking both before and after thermal cycling. These results demonstrate a surprising synergy between the cap layer and the base layer when the cap layer comprises an impact modified PMMA. For example, the forming temperature can be less than or equal to 100° C., specifically, less than or equal to 95° C., more specifically, less than or equal to 85° C., and even more specifically, less than or equal to 75° C. as well as any ranges or endpoints therebetween (e.g., temperatures of 76° C., 81° C., 92° C., etc.).

The multilayer sheets disclosed herein are capable of achieving a pencil hardness of greater than or equal to HB at cap layer thicknesses of greater than or equal to 20 micrometers, specifically, greater than or equal to 25 micrometers, more specifically, greater than or equal to 30 micrometers, and even more specifically, greater than or equal to 40 micrometers. The sheets disclosed herein offer a combination of properties such as clarity, printability, thermoformability, and hardness, as well as scratch, chemical, and impact resistance. The sheets disclosed herein can also advantageously be processed below the glass transition temperature of the cap layer and the base layer and still achieve a pencil hardness of greater than or equal to HB. For example, the glass transition temperature of PMMA is generally in the range of 100° C. to 101° C., while the glass transition temperature for a copolymer of PC/PCTG is generally in the range of 105° C. to 110° C. Thermoforming of the sheet can be performed at temperatures less than or equal to 100° C., specifically, less than or equal to 95° C., more specifically, less than or equal to 85° C., and even more specifically, less than or equal to 75° C. This is advantageous because it allows for the material to be processed below the glass transition temperatures of the both the materials of the base layer and the cap layer and with the use of a single manifold die rather than a multi-manifold die.

Ranges disclosed herein are inclusive and combinable (e.g., ranges of “up to about 25 wt %, or, more specifically, about 5 wt % to about 20 wt %”, is inclusive of the endpoints and all inner values of the ranges of “about 5 wt % to about 25 wt %,” etc.). “Combination” is inclusive of blends, mixtures, derivatives, alloys, reaction products, and so forth. Furthermore, the terms “first,” “second,” and so forth, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another, and the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The modifier “about” used in connection with a quantity is inclusive of the state value and has the meaning dictated by context, (e.g., includes the degree of error associated with measurement of the particular quantity). The suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the colorant(s) includes one or more colorants). Reference throughout the specification to “one embodiment”, “another embodiment”, “an embodiment”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and can or can not be present in other embodiments. In addition, it is to be understood that the described elements can be combined in any suitable manner in the various embodiments. As used herein, the term “(meth)acrylate” encompasses both acrylate and methacrylate groups. Compounds are described using standard nomenclature. For example, any position not substituted by any indicated group is understood to have its valency filled by a bond as indicated, or a hydrogen atom. A dash (“-”) that is not between two letters or symbols is used to indicate a point of attachment for a substituent. For example, —CHO is attached through carbon of the carbonyl group.

All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference.

While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

1. A sheet, comprising: a cap layer comprising an acrylic polymer, wherein the cap layer is 10% to 30% of an overall thickness and the overall thickness is 5 mil to 500 mil; and a base layer comprising a polycarbonate; wherein the cap layer and the base layer were co-extruded to form the sheet, which is thermoformable.
 2. The sheet of claim 1, wherein the sheet has a pencil hardness greater than or equal to HB.
 3. The sheet of claim 1, wherein the sheet has a pencil hardness greater than or equal to H.
 4. The sheet of claim 1, wherein the base layer comprises a copolycarbonate.
 5. The sheet of claim 2, wherein the base layer comprises a cycloaliphatic polyester copolymer and a polycarbonate, wherein the cycloaliphatic polyester copolymer is poly(1,4-cyclohexylene dimethylene co-ethylene terephthalate).
 6. The sheet of claim 1, wherein the cap layer is on and in contact with the base layer.
 7. The sheet of claim 1, wherein the overall thickness is 5 mil to 40 mil.
 8. The sheet of claim 1, wherein the sheet is thermoformed at a temperature below the glass transition temperatures of the acrylic polymer and the polycarbonate.
 9. The sheet of claim 5 wherein the blend comprises 20 wt % to 50 wt % cycloaliphatic polyester, balance polycarbonate.
 10. The sheet of claim 1, wherein the acrylic polymer comprises an alkyl(meth)acrylate.
 11. The sheet of claim 10, wherein the alkyl(meth)acrylate comprises a poly(methyl)methacrylate.
 12. The sheet of claim 11, wherein the poly(methyl)methacrylate has a haze value of less than or equal 5% as determined according to ASTM D1003-00.
 13. A sheet, comprising: a cap layer comprising an acrylic polymer, wherein the cap layer is 10% to 30% of an overall thickness and the overall thickness is 5 mil to 500 mil; and a base layer comprising a cycloaliphatic polyester copolymer and a polycarbonate, wherein the cycloaliphatic polyester copolymer is poly(1,4-cyclohexylene dimethylene co-ethylene terephthalate); wherein the cap layer and base layer were co-extruded to form the sheet which is thermoformable; and wherein the sheet has a pencil hardness greater than or equal to HB.
 14. The sheet of claim 13, wherein the acrylic polymer comprises an alkyl(meth)acrylate.
 15. The sheet of claim 14, wherein the acrylic polymer comprises poly(methyl)methacrylate.
 16. A method for making an article, comprising: melting an acrylic polymer in an extruder; forming a molten mixture comprising a polycarbonate in an extruder; co-extruding the acrylic polymer and the molten mixture to form a sheet which is thermoformable, wherein the molten mixture forms a base layer and the acrylic polymer forms a cap layer on the base layer; wherein the cap layer is 10% to 30% of an overall sheet thickness; and wherein the sheet has a pencil hardness greater than or equal to HB.
 17. The method of claim 16, further comprising thermoforming the sheet at a temperature below the glass transition temperatures of the acrylic polymer and the polycarbonate.
 18. The method of claim 16, wherein the acrylic polymer comprises an alkyl(meth)acrylate.
 19. The method of claim 16, wherein the overall sheet thickness is 3 mil to 20 mil.
 20. The method of claim 16, wherein the cap layer is co-extruded on and in contact with the base layer. 